The present disclosure is in the technical field of frequency-modulated continuous-wave (FMCW) light detection and ranging (LIDAR).
Generally, FMCW LIDAR systems sense range by measuring interference between optical signals from a local path and a target path. By sweeping the frequency of a laser, the interference signal becomes an oscillation with a frequency proportional to target distance. FMCW lasers may be modulated to have a linear frequency sweep from lower frequency to higher frequency, and then from higher frequency to lower frequency, in a triangular fashion.
Moving reflectors may cause a shift in the measured frequency proportional to the velocity of the reflector. To tell the difference between the effect of reflector's distance and velocity, one may measure the interference frequency during the positive laser sweep, and then the interference frequency during the negative frequency sweep.
The speed with which measurements are attained may be important, and the method of making two measurements to obtain velocity may take twice as long as the method of only measuring range. Thus, a method to use multiple frequency-modulated lasers with complementary frequency sweeps combined with a method to discriminate the complementary frequency sweeps may enhance the measurement speed of a distance and velocity LIDAR sensor. The method of discriminating the complementary frequency sweeps resolves ambiguity problems where the time delay and frequency shift effects cannot be sufficiently decoupled.
Further, generally, FMCW LIDAR systems use swept-source lasers to measure distance and velocity. The frequency of a reflected signal may be proportional to a target's distance. Moving targets shift a reflected signal's frequency proportional to the velocity of the target due to the Doppler effect, which can be measured simultaneously.
Beam steering modules may scan laser beams across a target environment. Having multiple laser channels in an optical system may involve several scanning elements to capture a larger field of view (FOV). A scheme that would allow several laser beams to share scanning elements may help reduce the complexity and cost of the system. It would further reduce cost of the system by implementing such scheme on integrated photonic chips.